A pacemaker implanted in a patient assists in maintaining patient heart rate. The pacemaker, a battery-powered device, detects the natural heart rate and supplements the natural heart rate when necessary, e.g., stimulating additional heartbeats to maintain a given heart rate. Pacemakers provide a variety of functions specific to a given patient's condition, e.g., stimulating the atrium, ventricle or both chambers. For purposes of the present invention, however, the pacemaker stimulates individual heartbeats when required and entirely "captures" the heart when stimulating every heartbeat. Doctors intermittently monitor the condition of patients and of implanted pacemakers to ensure a stable patient condition and a working and reliable pacemaker.
A pacemaker monitor transmitter (PMT), used by patients with an implanted pacemaker, determines patient heart and pacemaker condition. The pacemaker monitor transmitter connects to the patient with electrodes and monitors the patient's heart electrical activity (EKG) as well as certain other pacemaker functions. Some pacemakers, for example, respond to a magnetic field by "capturing" the heart and establishing a heartbeat at a given "magnetic" rate, i.e., bypasses demand mode. A patient triggers a pacemaker into such "magnetic" mode by placing a strong magnet near the pacemaker. Monitoring EKG activity during the magnetic mode indicates the condition of the pacemaker. The pacemaker may indicate battery condition, for example, by modifying the width of stimulation pulses generated by the pacemaker. In particular, when the battery goes low, stimulation pulse width increases. Pulse width data, therefore, is an important measurement taken during evaluation of a given pacemaker. Other pacemakers indicate a low battery condition by modification to the "magnetic" rate. When a battery low condition exists, the pacemaker "magnetic" rate may change, e.g., decreases by a given percentage.
A pacemaker monitor transmitter verifies that the pacemaker is programmed appropriately and that it can capture the heart, and determines the battery condition of the pacemaker. These tests can be performed in a physician's office, preferably every one to three months. Many physicians, especially in rural settings, do not want the patient to travel to the doctor's office to conduct these tests. Fortunately, these tests can be conducted remotely, i.e., via telephone connection between the pacemaker monitor transmitter and a receiving station at the doctor's office. This eliminates patient travel to the doctor's office.
Unfortunately, people with implanted pacemakers are usually elderly. These elderly patients, sometimes nervous and confused, must conduct pacemaker and heart monitoring sessions. Generally, the patient calls the doctor's office and performs certain actions in manipulation of the pacemaker monitor transmitter and pacemaker itself to stimulate the heartland pacemaker into appropriate modes for evaluation. Several steps are executed, and a person at the remote receiving station typically guides the patient through the session by voice instruction.
Early pacemaker monitor transmitters were chest-held units. Patients held the pacemaker monitor transmitter against their chest, held a telephone on the pacemaker monitor transmitter, held a magnet over the pacemaker, and remained as still as possible to minimize body motion artifact during transmission. If the patient does not remain still, body motion produces incorrect EKG data. More recent pacemaker monitor transmitter devices, however, comprise a self-contained box for all electrical components, a telephone cradle, and wires connected to electrodes contacting the patient. This more recent type of a pacemaker monitor transmitter reduces patient anxiety for its relatively more convenient use, but still exhibits certain problems.
A common problem with existing pacemaker monitor transmitter devices is difficulty in communicating with elderly patients. When problems occur, the receiving station must talk to the patient to instruct the patient step-by-step through the monitoring session. To obtain the patient's attention, a signal from the receiving center to the pacemaker monitor transmitter generates a tone at the telephone cradle or receiving unit. Unfortunately, such tones are for many patients difficult to hear. The tone delivered to the pacemaker monitor transmitter also activates a patient alert light on the device. When the patient sees this light, the patient picks up the telephone to interact verbally with the remote center. Some configurations require that a person at the remote station yell into the telephone with the hope that the patient hears the person yelling. Furthermore, verbal communication is hampered by the ongoing data transmission present on the telephone connection. The volume of the data transmission often overrides tone signals and voice communication on the telephone connection.
Another problem with existing pacemaker monitor transmitters is patient activity corrupting the EKG signal and rendering a reading useless. An EKG reading can in some cases be obtained in several seconds, whereas in other situations with excess motion artifact noise, the EKG readings may take 30 to 40 seconds. This indeterminacy furthers patient anxiety in not knowing when a given EKG reading is complete and when a new instruction need be received verbally from the remote station. In other words, often the patient does not know when a test step is complete and the person at the remote station cannot get the patient's attention.
Finally, data transmitted to the receiving station may take a variety of formats. Many receiving center stations collect data according to several data formats. Preferably, however, the receiving station need not be adjusted to match an incoming stream of data from a pacemaker monitor transmitter.
Accordingly, it is desirable to improve operation of a pacemaker monitor transmitter by reducing or eliminating patient anxiety and making more simple the process of conducting heart and pacemaker evaluation sessions. To the extent that patient anxiety and motion artifact can be minimized, an acceptable EKG reading may be taken more efficiently and thereby support the goal of monitoring at a remote station the condition of the patient's heart and pacemaker.